Copy `remap` from `forest`

[igorkamyshev]

Before

const Comp = relfect({
 view: ViewComp,
 bind: {
   prop: $value.map(value => value.part)
 }
})

after

const Comp = relfect({
 view: ViewComp,
 bind: {
   prop: remap($value, 'part')
 }
})